Tree-Type Broadcast System, Reconnection Process Method, Node Device, Node Process Program, Server Device, and Server Process Program

1. A node device in a tree-type broadcast system formed by participation of a plurality of node devices that form a plurality of hierarchy levels, wherein a broadcast device is located at a top of the plurality of hierarchy levels and the node devices are connected in a tree-like shape through a communication circuit to enable information broadcasted by the broadcast device to be sequentially transferred from a node device among the plurality of node devices located at a higher hierarchy level to a node device among the plurality of node devices located at a lower hierarchy level, the node device comprising: a connection information receiving unit configured to receive connection destination candidate information, which is broadcasted from the broadcast device, is sequentially transferred through the plurality of node devices from the node device located at an upper hierarchy level to the node device located at a lower hierarchy level, and indicates from among the plurality of node devices one or more node devices to be reconnection destination candidates, including at least network address information of the node devices to be the reconnection destination candidates; a reconnection destination candidate specifying unit configured to specify one or more node devices out of the node devices to be reconnection destination candidates indicated in the received connection destination candidate information suitable for attribute information of the node device; a reconnection destination candidate memory unit configured to memorize at least network address information of specified node devices, the specified node devices being the node devices out of the node devices to be reconnection destination candidates specified by the reconnection destination candidate specifying unit; and a connection processing unit configured to carry out a connection process of selecting one node device as a reconnection destination node device out of the specified node devices memorized in the reconnection destination candidate memory unit and to connect to the reconnection destination node device based on the network address information of the reconnection destination node device, in response to determining that the node device is newly reconnected to the reconnection destination node device.

2. The node device according to claim 1 , further comprising: a connection destination candidate information transfer unit configured to transfer the connection destination candidate information received by the connection information receiving unit from a node device among the plurality of node devices located in a higher hierarchy level than the node device to a node device among the plurality of node devices located in a lower hierarchy level than the node device.

3. The node device according to claim 1 , further comprising: an allowable number judgment unit configured to judge whether a number of node devices located in a lower hierarchy level connected to the node device reaches an allowable number of the node devices connectable to the lower hierarchy level of the node device, wherein the connection destination candidate information transferring unit transfers the received connection destination candidate information to node devices located in a lower hierarchy level connected to the node device, in response to judging that the number of the node devices reaches the allowable number by the allowable number judgment unit.

4. The node device according to claim 1 , wherein the connection destination candidate information includes information indicative of a hierarchy level in the system of node devices to be the reconnection destination candidates, the attribute information includes information indicative of a hierarchy level in the system of the node device, and the reconnection destination candidate specifying unit specifies node devices located in a hierarchy level higher than or the same as the node device as the specified node devices, based on the information indicative of the hierarchy level, among node devices to be the reconnection destination candidates in the received connection destination candidate information.

5. The node device according to claim 1 , wherein the connection destination candidate information includes information indicative of a communication method in the system of the node devices to be the reconnection destination candidates, the attribute information includes information indicative of a communication method of the system of the node device, and the reconnection destination candidate specifying unit specifies node devices applicable to the communication method of the node device as the specified node devices, based on the information indicative of the communication method, among node devices to be the reconnection destination candidates in the received connection destination candidate information.

6. The node device according to claim 1 , wherein the connection destination candidate information indicates a plurality of node devices to be reconnection destination candidates, and the reconnection destination candidate specifying unit randomly specifies node devices of number smaller than an appropriate number as the specified node devices, among node devices to be the reconnection destination candidates in the received connection destination candidate information.

7. The node device according to claim 1 , wherein the reconnection destination candidate memory unit memorizes the node device attribute information in addition to network address information of the specified node devices, the node device, further comprising: an update information receiving unit configured to receive update information which is broadcasted from a node device among the plurality of node devices located in a higher hierarchy level than the node device which is currently connected to the node device or from the broadcast device and which includes attribute information after the change of a node device having attribute information changed by reconnection in the tree-type broadcast system; and an attribute information update unit configured to update attribute information memorized in the reconnection destination candidate memory unit, based on attribute information included in the update information.

8. The node device according to claim 1 , wherein the connection destination candidate information is generated by a server device managing connection modes of node devices in the tree-type broadcast system and provided to the broadcast device, the node device, further comprising: a report information receiving unit that receives report information indicative of a participation report in the tree-type broadcast system or a withdrawal report from the tree-type broadcast system, which is sent from a node device among the plurality of node devices in a lower hierarchy level connected to the node device; a report information storing unit that stores the received report information; and a report information sending unit that sends the report information stored every predetermined time period to the server device in a case where the node device is a representative node device sending the report information to the server device as a representative, and which sends the received report information to a node device among the plurality of node devices in a higher hierarchy level connected to the node device in a case where the node device is not the representative node device.

9. The node device according to claim 1 , further comprising: an allowable number judgment unit configured to judge whether a number of node devices located in a lower hierarchy level connected to the node device reaches an allowable number of the node devices connectable to the lower hierarchy level of the node device; and a connection information storing unit that stores the received connection destination candidate information for a predetermined time in order to transfer the received connection destination candidate information to a node device among the plurality of node devices to be connected later to the node device in the lower hierarchy level.

10. A non-transitory computer-readable medium recording a reconnection process program to be performed by a node device in a tree-type broadcast system which is formed by participation of a plurality of node devices that form a plurality of hierarchy levels, wherein a broadcast device is located at a top of the plurality of hierarchy levels and the node devices are connected in a tree-like shape through a communication circuit to enable information broadcasted by the broad device to be sequentially transferred from a node device located at a higher hierarchy level to a node device located at a lower hierarchy level, the program comprising receiving connection destination candidate information, which is broadcast from the broadcast device and sequentially transferred from the node device located at the higher hierarchy level to the node device located at the lower hierarchy level, indicating node devices to be reconnection destination candidates, and including at least network address information of the node devices to be the reconnection destination candidates; specifying in a reconnection destination candidate specifying unit one or more node devices out of the node devices to be reconnection destination candidates indicated in the received connection destination candidate information suitable for attribute information of the node device; memorizing in a reconnection destination candidate memory unit at least network address information of specified node devices, the specified node devices being the node devices out of the node devices to be reconnection destination candidates specified by the reconnection destination candidate specifying unit; and carrying out a connection process of selecting one node device as a reconnection destination node device out of the specified node devices memorized in the reconnection destination candidate memory unit and connecting to the reconnection destination node device, in response to determining that the node device is newly reconnected to the reconnection destination node device.

11. A tree-type broadcast system formed by participation of a plurality of node devices that form a plurality of hierarchy levels, wherein a broadcast device is located at a top of the plurality of hierarchy levels and the node devices are connected in a tree-like shape through a communication circuit to enable information broadcasted by the broadcast device to be sequentially transferred from a node device among the plurality of node devices located at a higher hierarchy level to a node device among the plurality of node devices located at a lower hierarchy level, the server device managing connection modes of the node devices in the tree-type broadcast system comprising: a connection destination candidate information generating unit configured to generate connection destination candidate information which indicates one or more node devices to be reconnection destination candidates of a node device in the tree-type broadcast system and which includes at least network address information of the node devices to be reconnection destination candidates, based on information indicative of connection modes; and a connection destination candidate information sending unit configured to send the generated connection destination candidate information and broadcast instruction information indicative of broadcast instruction of the connection destination candidate information to the broadcast device, the node device in the tree-type broadcast system comprising: a connection information receiving unit configured to receive connection destination candidate information, which is broadcasted from the broadcast device, is sequentially transferred through the plurality of node devices from the node device located at an upper hierarchy level to the node device located at a lower hierarchy level, and indicates from among the plurality of node devices one or more node devices to be reconnection destination candidates, including at least network address information of the node devices to be the reconnection destination candidates; a reconnection destination candidate specifying unit configured to specify one or more node devices out of the node devices to be reconnection destination candidates indicated in the received connection destination candidate information suitable for attribute information of the node device; a reconnection destination candidate memory unit configured to memorize at least network address information of specified node devices, the specified node devices being the node devices out of the node devices to be reconnection destination candidates specified by the reconnection destination candidate specifying unit; and a connection processing unit configured to carry out a connection process of selecting one node device as a reconnection destination node device out of the specified node devices memorized in the reconnection destination candidate memory unit to connect to the connection destination node device based on the network address information of the reconnection destination node device, in response to determining that the node device is newly reconnected to the reconnection destination node device.

12. A reconnection process method of a node device in a tree-type broadcast system formed by participation of a plurality of node devices that form a plurality of hierarchy levels, wherein a broadcast device is located at a top of the plurality of hierarchy levels and the node devices are connected in a tree-like shape through a communication circuit to enable information broadcasted by the broadcast device to be sequentially transferred from a node device among the plurality of node devices located at a higher hierarchy level to a node device among the plurality of node devices located at a lower hierarchy level, the method comprising: receiving connection destination candidate information, which is broadcast from the broadcast device and sequentially transferred from the node device located at the higher hierarchy level to the node device located at the lower hierarchy level, indicating node devices to be reconnection destination candidates, and including at least network address information of the node devices to be the reconnection destination candidates; specifying in a reconnection destination candidate specifying unit one or more node devices out of the node devices to be reconnection destination candidates indicated in the received connection destination candidate information suitable for attribute information of the node device receiving connection destination candidate information; memorizing in a reconnection destination candidate memory unit at least network address information of specified node devices, the specified node devices being the node devices out of the node devices to be reconnection destination candidates specified by the reconnection destination candidate specifying unit; and carrying out a connection process of selecting one node device as a reconnection destination node device out of the specified node devices memorized in the reconnection destination candidate memory unit and connecting to the reconnection destination node device, in response to determining that the node device is newly reconnected to the reconnection destination node device.